Optimization of 2-Aminoquinazolin-4-(3H)-one Derivatives as Potent Inhibitors of SARS-CoV-2: Improved Synthesis and Pharmacokinetic Properties

We previously reported the potent antiviral effect of the 2-aminoquinazolin-4-(3H)-one 1, which shows significant activity (IC(50) = 0.23 μM) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with no cytotoxicity. However, it is necessary to improve the in vivo pharmacokinetics of compound 1 because its area under the curve (AUC) and maximum plasma concentration are low. Here, we designed and synthesized N-substituted quinazolinone derivatives that had good pharmacokinetics and that retained their inhibitory activity against SARS-CoV-2. These compounds were conveniently prepared on a large scale through a one-pot reaction using Dimroth rearrangement as a key step. The synthesized compounds showed potent inhibitory activity, low binding to hERG channels, and good microsomal stability. In vivo pharmacokinetic studies showed that compound 2b had the highest exposure (AUC(24h) = 41.57 μg∙h/mL) of the synthesized compounds. An in vivo single-dose toxicity evaluation of compound 2b at 250 and 500 mg/kg in rats resulted in no deaths and an approximate lethal dose greater than 500 mg/kg. This study shows that N-acetyl 2-aminoquinazolin-4-(3H)-one 2b is a promising lead compound for developing anti-SARS-CoV-2 agents.